public bool Update(PhoneStatistic phoneStatistics)
 {
     bool canUpdate = (_fileRepository.GetById(phoneStatistics.Id) != null);
     if (canUpdate)
     {
         _fileRepository.Upsert(phoneStatistics);
     }
     return canUpdate;
 }
 public PhoneStatistic Create(string phoneId, string targetPhone, DateTime dateTime, int durationSecs, int pricePerMinute)
 {
     var phoneStat = new PhoneStatistic(phoneId, targetPhone, dateTime, durationSecs, pricePerMinute);
     _fileRepository.Upsert(phoneStat);
     return phoneStat;
 }